IMMUNITY AND SUSCEPTIBILITY. 121 



/. Inert particles are sometimes capable of producing 

 very remarkable protective reactions when mixed with 

 the toxins and injected into the cellular tissues. 



Staudensky 1 has found that if ordinary commercial 

 carmin is mixed with tetanus toxin in the proportion of 

 0.5 gram to 10 cubic centimeters, ten fatal doses can be 

 administered to a guinea pig without resulting harm. 

 Interestingly enough, if the solution of carmin is heated 

 to 6o°-ioo° C, it loses its protective effect, though when 

 dry carmin is heated in a sealed tube it is unchanged. 

 When the mixture is kept for twenty-four hours it again 

 becomes toxic, and if fresh mixtures are filtered free from 

 the carmin its effect is lost. The toxin is, therefore, not 

 destroyed by the carmin. Microscopic examination of the 

 inflammatory exudate found at the seat of inoculation 

 shows large numbers of leukocytes, which may be respon- 

 sible for the toxin destruction. 



Immunization. — The process of rendering an animal 

 immune is described as immunization, though at the pres- 

 ent time this term is being more and more restricted to 

 those cases in which the animal attains a high degree of 

 immunity by a gradual process which I have already de- 

 scribed as forced immunity. In the last few years this sub- 

 ject has been very carefully studied in its most important 

 relation to the therapeutic serums. These remedies are all 

 produced by the same general management of the animal, 

 though it may be that in one case some alkaloidal tox- 

 albumin, in others some bacterial toxin, and in still 

 others some sterilized culture, attenuated culture, or 

 living virulent culture of bacteria is employed. An 

 appropriate animal is selected and carefully examined to 

 exclude diseased or other unfavorable conditions. It is 

 then given a very small dose of the toxin (for convenience I 

 shall refer to whatever preparation the animal receives as 

 toxin), from the effect of which it is allowed to completely 

 recover. If the effect has been too active, the toxin can 

 be modified by adding some of the trichlorid of iodin 



1 Annates de V Inst. Pasteur, Feb. 25, 1899, p. 126. 



